Semiconductor chip repair by stacking of a base semiconductor chip and a repair semiconductor chip

ABSTRACT

In one aspect, a method of enhancing semiconductor chip process variability and lifetime reliability through a three-dimensional (3D) integration applied to electronic packaging is disclosed. Also provided is an arrangement for implementing the inventive method. In another aspect, a method and on-chip controller are disclosed for enhancing semiconductor chip process variability and lifetime reliability through a three-dimensional (3D) integration applied to electronic packaging. Also provided is an on-chip reliability/variability controller arrangement for implementing the inventive method. In yet another aspect, base semiconductor chips, each comprising a plurality of chiplets, are manufactured and tested. For a base semiconductor chip having at least one non-functional chiplet, at least one repair semiconductor chiplet chiplet is vertically stacked. A functional multi-chip assembly is formed, which provides the same functionality as a base semiconductor chip in which all chiplets are functional.

The present application is a continuation-in-part of, is related to, andclaims the benefit of priority from, invented-by-the-same-inventors andcommonly assigned U.S. application Ser. No. 11/947,207, filed on Nov.29, 2007 and now abandoned, and Ser. No. 11/948,376, filed on Nov. 30,2007 and now abandoned. The contents of U.S. application Ser. Nos.11/947,207 and 11/948,376 are expressly incorporated herein. The presentapplication is also related to a commonly assigned and co-pending U.S.application Ser. No. 12/041,878 filed on Mar. 4, 2008, the contents ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method for enhancing semiconductorchip process variability and lifetime reliability throughthree-dimensional (3D) integration and an arrangement for implementingthe inventive method, and a control method and on-chip controller forenhancing semiconductor chip process variability and lifetimereliability through the intermediary of three-dimensional (3D)integration. Further, the present invention generally relates tosemiconductor structures, and particularly to a multi-chip stackedsemiconductor structure providing improvement in yield and methods ofmanufacturing the same.

BACKGROUND OF THE INVENTION

Increased requirements in power density and technology scaling forelectronic package components have encountered considerably increasedexisting reliability problems in recent years, as a result of whichlifetime reliability and process variation has already been elevated tothe “critical challenges” category according to ITRS 2005 in thetechnology.

Chip lifetime reliability has traditionally been ensured through processqualification and sorting out of defective chips through accelerateddegradation techniques like process burn-in. The utilization ofstructural duplication is considered as another standard technique fordealing with lifetime reliability issues; however, the correspondingrequired overhead in terms of increased cost, manufacturing area andcomplexity, generally limits the extent of applicability thereof inpractice. Similarly, the traditional burn-in process that is used toaccelerate extrinsic failures is reaching a point where it is raising anumber of complications and is becoming more difficult to implement witheach successive process generation. In some instances, burn-in isbelieved to cause lifetime reliability problems itself, as a result ofwhich, there has been an increased degree of interest in developingalternative techniques for improving the chip lifetime reliabilitywithout the burn-in process in recent years.

There is a significant amount of cost associated with the processvariation in technologies, especially at levels of 32 nm and below. Lostyield due to process variability causes millions of dollars in wastedexpenditures every year per production line. There is significant costand problems associated with lost yield due to process variation incurrent and next generation technologies. These include timing andassociated functionality problems, performance reduction due to thetiming changes, increase in chip footprint due to the additional blocks,ability to handle only single fault and single type of fault due to lackof intelligence in the current approaches to dealing with variability.

In order to provide clear advantages over the current state of thetechnology, in accordance with the invention, there is proposed atechnique that is adapted to alleviate lifetime reliability and processvariability issues through the intermediary of three-dimensional (3D)integration. Even though the motivation for 3D integration has beenlargely interconnect-driven and packaging-oriented, 3D integration canprovide further broader advantages when effectively utilized.

Chip yield, which is the fraction of functional chips among allmanufactured chips, is a key factor in determining chip cost. From amanufacturing point of view, per-wafer production cost of semiconductorchips cannot be lowered below a certain level. Since the totalproduction cost must be recouped from the sale of functional chips, alow chip yield invariably drives up the unit cost of the chip.

State-of-the-art semiconductor chips that provide superior performanceoften run into a high production cost due to low chip yield. This isbecause state-of-the-art semiconductor chips, in order to deliversuperior performance than more common economical chips, tend to utilizea large chip area as well as aggressively scaled lithographic dimensionsand processing techniques that have not fully matured or stabilized.Thus, the more aggressive the unit process technology employed inmanufacturing a chip, and the larger the area of the chip, the lower thechip yield and the higher the cost of the chip.

In order to improve chip yield, redundancy repair components are oftenfabricated on a chip. This is almost universally done for arraystructures such as dynamic random access memory (DRAM) arrays and staticrandom access memory (SRAM) arrays. Incorporation of redundant rows orredundant columns is easy to implement in an array structure.

For logic blocks, redundancy is much harder to implement sincecomponents of logic blocks are much less repetitive. Prediction of ahigh failure rate area is mostly a futile exercise since most of thelogic block components have insignificant failure rates. Thus, buildingredundancy for logic blocks is much less effective than for an arraystructure, as well as requiring much more area than redundancy repaircomponents for the array structure. In other words, the area penaltyassociated with building redundancy repair components for logic blocksis unacceptably high.

Normal chips containing multiple processor cores on a semiconductorsubstrate could include extra processor cores for redundancy repair toimprove yield. However, the total area of the extra processor coreincluding the areas of caches and bus interconnect logic circuits issubstantial for each extra processor core. Further, considering that thecaches and the bus interconnect logic circuits typically have a highyield, the areas occupied by the caches and the bus interconnect logiccircuits are wasted area that typically does not contribute to improvedyield yet increases the total chip area.

Further, design requirements typically call for a number of processorcores that is a power of two, i.e., 2, 4, 8, etc., which typically fitsinto natural floor planning pattern for chips. Adding extra processorcores for redundancy repair generally breaks this natural floor planningpattern. For these reasons, addition of extra processor cores into asemiconductor chip is, in general, problematic.

However, providing a mechanism for repairing a chip has grown inimportance since the number of processor cores per chip continues toincrease. “All good chips” in which all processor cores are functionalbecomes more challenging with the increase in the number of processorcores.

In view of the above, there exists a need to provide improved yield to asemiconductor chip having multiple processor cores.

Specifically, there exists a need to provide a structure having a repaircapability to semiconductor chips having multiple processor cores andmethods of manufacturing the same.

SUMMARY OF THE INVENTION

According to one aspect of the present disclosure, in order to implementthe foregoing, there is provided a method for enhancing the lifetimereliability and process variability through effective use ofthree-dimensional integration technology. An auxiliary so-called healinglayer is attached to an original processor die through 3D integration.This one-fits-all auxiliary layer can solve any reliability orvariability problem automatically at run time, and preserves thesynchronous timing while potentially improving the performance of afaulty chip compared to the baseline. More extensively, proposed is anintelligent on-chip controller which manages the redundancy in theauxiliary layer, including exact replicas of number of critical blocks;generic and configurable logic resources; configurable wiring andhigh-bandwidth low-latency interconnect to the primary layer. Theinvention, thus, focuses on utilizing these resources through 3Dintegration in order to improve upon lifetime reliability andvariability.

One primary aspect of the invention resides in utilizing the available3D redundancy, by dynamically adjusting the processor resources on bothlayers, i.e., primary and device layers, simultaneously including logicand interconnectivity in order to bring the system to a state at whichit can achieve at least the same or improved performance over thebaseline. High-end server systems are good candidates for this“healing/compensating layer technique”. Not only does the additionalmemory hierarchy in this layer provide performance improvement, thereconfigurable redundancy enables enhanced lifetime reliability inrecovering from a wide range of faults.

According to another aspect of the present disclosure, the presentinvention is directed to providing an on-chip controller adapted tofacilitate implementing a method to alleviate lifetime reliability andprocess variability issues through three-dimensional integration.Three-dimensional integration has shown significant potential forimproving the integrated circuit design in the past years. Even thoughthe motivations for 3D has been largely interconnect driven andpackaging, 3D integration can provide further advantages if it iseffectively utilized.

Concerning the foregoing, the invention is directed to a method forenhancing the lifetime reliability and process variability througheffective use of three-dimensional integration technology. An auxiliaryso-called healing layer is attached to an original processor die through3D integration. This one-fits-all auxiliary layer can solve anyreliability or variability problem automatically at run time, andpreserves the synchronous timing while potentially improving theperformance of a faulty chip compared to the baseline. Proposed is anintelligent on-chip controller which manages the redundancy in theauxiliary layer, including exact replicas of number of critical blocks;generic and configurable logic resources; configurable wiring andhigh-bandwidth low-latency interconnect to the primary layer. Theinvention, thus, focuses on utilizing these resources through 3Dintegration in order to improve upon lifetime reliability andvariability, but not claiming the invention of an additional devicelayer or the hardware units in this layer.

The auxiliary or second device layer includes: (i) an on-chipreliability/variability controller, which is capable of monitoringon-chip resources, recovering from faults and process variabilityinduced differences through activating/deactivating/configuring one ormore of the logic or memory units or interconnect on the chip; (ii)exact replicas of critical blocks on the second layer (whereby bothlayers have matching floor plans, where the duplicates are locatedvertically on top of the originals), but not all units in amicroprocessor are of equal criticality. Units such as register files,issue or fetch logic are of higher importance compared to caches andpredictors, for which faults can be tolerated to a certain extent; (iii)generic logic, which is to be used as redundancy for variousreconfigurable redundancy enables enhanced lifetime reliabilityrecovering from a wide range of faults.

In one embodiment of the present disclosure, an on-chip method utilizinga controller for enhancing semiconductor chip process variability andlifetime reliability through a three-dimensional integration applied toelectronic packaging is provided. The method includes:

-   -   (a) providing a first semiconductor chip essentially consisting        of a microprocessor, a plurality of performance and memory        resources, including selectively functional units, control        macros, elements of data flow, register files and memory arrays;    -   (b) providing a second semiconductor chip in a superimposed        arrangement over the first semiconductor chip, the second        semiconductor chip including an on-chip controller and redundant        resources actuatable upon recognition of a faulty resource or        plurality of faulty resources on the first semiconductor chip;    -   (c) configuring at least one of the redundant resources on the        second semiconductor chip as a performance enhancer for at least        one of the resources on the first semiconductor chip; and    -   (d) incorporating redundancies on the second semiconductor chip        thereon for critical macros on the first semiconductor chip        selectively comprising vectors, fixed or floating point        execution blocks, auxiliary pipelines and diverse component        units.

The method can further include having an on-chip controller activate andrewire any encountered on-chip redundancy including configurableredundancies depending upon current malfunctions and/or faults in thesemiconductor chip.

In another embodiment of the present disclosure, an on-chip controllerarrangement for enhancing semiconductor chip process variability andlifetime reliability through a three-dimensional integration applied toelectronic packaging. The arrangement includes:

-   -   (a) a first semiconductor chip essentially consisting of a        microprocessor, a plurality of performance and memory resources,        including selectively functional units, control macros, elements        of data flow, register files and memory arrays;    -   (b) a second semiconductor chip being located in a superimposed        arrangement over the first semiconductor chip, the second        conductor chip including an on-chip controller and redundant        resources actuatable upon recognition of a faulty resource or        plurality of faulty resources on the first semiconductor chip;    -   (c) at least one of the redundant resources on the second        semiconductor chip being configured as a performance enhancer        for at least one of the resources on the first semiconductor        chip; and    -   (d) redundancies on the second semiconductor chip being        incorporated for critical macros on the first semiconductor chip        selectively comprising vectors, fixed or floating point        execution blocks, auxiliary pipelines and diverse component        units.

In yet another embodiment, the on-chip controller activates and rewiresany encountered on-chip redundancy including configurable redundanciesdepending upon current malfunctions and/or faults in the semiconductorchip.

According to yet another aspect, the present invention addresses theneeds described above by providing a multi-chip semiconductor assemblyin which loss of functionality through a defective chiplet within a basesemiconductor chip is compensated for with a repair semiconductor chipproviding the functionality of the chiplet, and methods of manufacturingthe same.

In the present invention, base semiconductor chips, each comprising aplurality of chiplets, are manufactured and tested. For a basesemiconductor chip having at least one non-functional chiplet, at leastone repair semiconductor chiplet, which provides the same functionalityas one of the at least one non-functional chiplet is designed toprovide, is vertically stacked. The at least one repair semiconductorchiplet provides the functionality that the at least one non-functionalchiplet is designed to provide to the base semiconductor chip. Thedefects in the functionality of the at least non-functional chiplet arecured through the at least one repair semiconductor chiplet, and thus, afunctional multi-chip assembly is formed, which provides the samefunctionality as a base semiconductor chip in which all chiplets arefunctional. In case a first attempt to repair the base semiconductorchip by stacking repair semiconductor chips is unsuccessful, additionalrepair semiconductor chips may be subsequently stacked to fully repairthe base semiconductor chip.

According to the present invention, a method of forming a multi-chipassembly of semiconductor chips is provided, which comprises:

forming a base semiconductor chip comprising a plurality of chipletsincluding at least one non-functional chiplet;

forming at least one repair semiconductor chip, wherein each the atleast one repair semiconductor chip includes a functional chipletproviding a same functionality as one of the at least one non-functionalchiplet is designed to provide; and

vertically stacking the at least one repair semiconductor chip on thebase semiconductor chip to form a multi-chip assembly, wherein themulti-chip assembly provides a same functionality as the basesemiconductor chip is designed to provide.

In one embodiment, the plurality of chiplets includes at least two of aprocessor core chiplet, a static random access memory (SRAM) chiplet, anembedded dynamic random access memory (eDRAM) chiplet, a cache memorychiplet, a non-volatile memory chiplet, a programmable gate array (PGA)chiplet, a peripheral circuitry chiplet, an input/output controlchiplet, a built-in-self-test (BIST) chiplet, a memory controllerchiplet, a power supply bus chiplet, a ground bus chiplet, and a signalbus chiplet.

In another embodiment, each of the functional chiplet in the repairsemiconductor chip has substantially the same design layout as one ofthe at least one non-functional chiplet.

In even another embodiment, each of the functional chiplet comprises aset of through-substrate vias formed within a substrate, wherein the setof through-substrate vias provides electrical connection between thefunctional chiplet and the base semiconductor chip.

In yet another embodiment, each of the repair semiconductor chipconsists of a functional chiplet having substantially the same designlayout as one of the at least one non-functional chiplet.

In still another embodiment, a design layout of the each of thefunctional chiplet in the repair semiconductor chip is a mirror image ofa design layout of one of the at least one non-functional chiplet.

In still yet another embodiment, the base semiconductor chip and the atleast one repair semiconductor chip are stacked back to back by C4bonding which provides electrical connection between the functionalchiplet and the base semiconductor chip.

In a further embodiment, each of the repair semiconductor chip consistsof a functional chiplet having the mirror image of the design layout ofone of the at least one non-functional chiplet.

In an even further embodiment, the method further comprisesmanufacturing and testing a plurality of base semiconductor chips,wherein the base semiconductor chip is identified when test dataindicates that the at least one non-functional chiplet in the basesemiconductor chip is non-functional.

In a yet further embodiment, at least two repair semiconductor chips arevertically stacked directly above and/or below a non-functional chipletof the base semiconductor chip, wherein each of the at least two repairsemiconductor chip includes a chiplet designed to provide a samefunctionality as the non-functional chiplet in the base semiconductorchip.

In a still further embodiment, one of the at least two repairsemiconductor chips is stacked directly above the base semiconductorchip by C4 bonding, and wherein another of the at least two repairsemiconductor chips is stacked below the base semiconductor chip by aset of through-substrate vias in a substrate of the base semiconductorchip.

In a further embodiment, the vertically stacked at least one repairsemiconductor chip provides at least a fraction of functionality thatthe at least one non-functional chiplet is designed to provide.

In an even further embodiment, the vertically stacked at least onerepair semiconductor chip provides more functionality than thefunctionality that the at least one non-functional chiplet is designedto provide.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing is clearly emphasized by referring to the accompanyingdrawings. The inventive concept is illustrated on the parts and fullintegration of three-dimensional embodiments of an electronic package.

FIG. 1 shows a primary semiconductor chip and an auxiliary (orsecondary) semiconductor chip for incorporation into a three-dimensionalsemiconductor chip. The auxiliary chip incorporates duplicated resourcesalong with the regular logic; and

FIG. 2 illustrates, generally diagrammatically, an embodiment ofsuperimposed semiconductor chip layers for effectuating thethree-dimensional integration process; and

FIG. 3 illustrates another embodiment of the invention wherein anauxiliary semiconductor chip is placed in the middle of two primarysemiconductor chips forming a 3-layer three-dimensional semiconductorchip.

FIG. 4 illustrates a flow chart explanatory of the on-chip controllerfunctions; and

FIG. 5 shows the recovery schemes of the controller.

FIG. 6 is a schematic representation of the chip stacking process of thepresent invention.

FIG. 7 is a flow diagram showing the processing steps of the presentinvention.

FIGS. 8A and 8B are sequential cross-sectional views illustratingformation of a first exemplary multi-chip assembly according to a firstembodiment of the present invention.

FIGS. 9A and 9B are sequential cross-sectional views illustratingformation of a second exemplary multi-chip assembly according to asecond embodiment of the present invention.

FIGS. 10A and 10B are sequential cross-sectional views illustratingformation of a third exemplary multi-chip assembly according to a thirdembodiment of the present invention.

FIGS. 11A and 11B are sequential cross-sectional views illustratingformation of a fourth exemplary multi-chip assembly according to afourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As stated above, the present invention relates to a method for enhancingsemiconductor chip process variability and lifetime reliability throughthree-dimensional (3D) integration and an arrangement for implementingthe inventive method, and a control method and on-chip controller forenhancing semiconductor chip process variability and lifetimereliability through the intermediary of three-dimensional (3D)integration, and a multi-chip stacked semiconductor structure providingimprovement in yield and methods of manufacturing the same, which arenow described in detail with accompanying figures. As used herein, whenintroducing elements of the present invention or the preferredembodiments thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. Throughoutthe drawings, the same reference numerals or letters are used todesignate like or equivalent elements. Detailed descriptions of knownfunctions and constructions unnecessarily obscuring the subject matterof the present invention have been omitted for clarity. The drawings arenot necessarily drawn to scale.

As used herein, a “chiplet” denotes a subset of a semiconductor chip ofintegral construction. A semiconductor chip includes at least onechiplet, and may contain a plurality of chiplets. A chiplet is afunctional unit of a semiconductor chip, and is typically provided withan edge seal within the semiconductor chip and occupies a dedicated areaof the semiconductor chip without overlapping with any other chiplet.

Pursuant to the method for enhancing lifetime reliability and/orperformance that uses 3D integration, there are employed at least twochips where the first chip is a microprocessor. The second chip consistsof a set of execution/memory resources configurable as either redundantresource for the microprocessor and microcontroller for managing andreconfiguring the resources in response to detection of a need forreplacing a resource in the first chip in a sequence of steps where as afirst step the pool of existing execution or memory resources is scannedto find an eligible replacement for the resource marked for replacement.If the eligible resource is not available, one of the reconfigurableresources is configured to replace the resource that is marked forreplacement. Hereby, one or more of the execution/memory resources inthe second chip is configured to work as a performance enhancer for oneof the resources in the first chip (such as a second pipeline in theauxiliary device layer).

Referring in detail to FIG. 1 of the drawings, a diagrammaticimplementation 100 of the basic components of this invention ispresented: a floor plan of a primary semiconductor chip 101 and anauxiliary (or secondary) semiconductor chip 102.

The primary chip or layer 101 may be a regular two-dimensionalsemiconductor microprocessor chip, with additional and necessaryresources for 3D chip integration. The resources in the first chip maybe complete processor cores, functional units, control macros, elementsof the processor dataflow, register files, memory arrays, whereby thereis also provided in the auxiliary (or secondary) chip, redundancy forcritical macros, such as vector, fixed or floating point executionblocks, auxiliary pipelines, accelerator cores, as well as genericconfigurable logic such as filed programmable gate arrays andprogrammable logic macros, wherein the custom macros are embedded in theconfigurable fabric thereof. In the drawing of FIG. 1 of the primarychip 101, we only highlight on-chip blocks or structures 122, 128 whichmay have exact replicas on the secondary layer chip 102.

The auxiliary device layer or chip 102 includes: (i) On-chipreliability/variability controller 116: capable of monitoring on-chipresources, recovering from faults and process variability induceddifferences through activating/deactivating/configuring one or more ofthe logic or memory units or interconnect on the chip; (ii) Exactreplicas of critical blocks 122 on the first/primary chip layer, wherebyboth layers 101, 102 have matching floor plans, where the duplicates arelocated vertically on top of the originals. However, not all units in amicroprocessor are of equal criticality. Units such as register files,issue or fetch logic are of higher importance compared to cache memoryand other prediction structures whose faults can be tolerated to acertain extent; (iii) Generic logic 130: for use as redundancy forvarious faults (lookup tables of configurable sizes, stacks); (iv)Configurable logic 130: for use for multiple purposes (configured by theon-chip controller); (v) Configurable interconnect 128 (lateral andvertical) and switch boxes: for connecting/disconnecting the replica ororiginal blocks as well as using the generic or configurable logicblocks; and (vi) Additional memory elements 126 (SRAM, DRAM, eDRAM) andother structures 124 for performance improvement.

Referring now in detail to FIG. 2 of the drawings, the concept isrepresented on a 2-layer 3D embodiment 200, having first and secondlayers 101, 102. The second device layer 102 includes an on-chipvariability/reliability controller 116, as well as redundant resources218 that can be activated if a primary unit 220 in the first devicelayer 101 is faulty. The on-chip controller 116 activates any idleblocks while inactivating (turning off and by-passing) faulty units.Moreover, it includes performance-enhancing resources 122, 124, 126,128, 130, additional cache/memory hierarchy such as DRAM or SRAM as wellas monitoring and recovering capabilities.

The connection between the primary copy of a block and the redundancywhich is placed on the top layer 102 may be achieved through verticalinterconnects 128, such as TSVs (through-the-silicon-vias). Theconfigurable interconnect 128 can be adjusted to connect either copy ofthe fault domains to the rest of the chip in case of a fault. Thisconfiguration is achieved through the use of switch boxes ormultiplexers (not shown).

The floor plans of the primary and secondary chip layers 101, 102 matchin terms of critical block placement, such that for critical blocks thereplicas in the secondary chip 102 are located on top of the primaryunits in the primary chip 101. This approach provides significantreduction in the interconnect length and latency. As the distancesbetween 2 device layers can be 20-50 um in the current 3D integration,the vertical delay between the original and the redundant unit is lessthan FO4. Hence, the synchronous timing is preserved. Also, asynchronouscases are easily handled with the same scheme.

Referring now in detail to FIG. 3 of the drawings, the inventive conceptis further represented on a 3-layer 3D embodiment 300, having first 101,second 102 and third 101 layers. In this embodiment, one auxiliary (orsecondary) chip 102 is stacked in between two primary chips 101. Thesecond device layer 102 includes an on-chip variability/reliabilitycontroller 116, as well as a configurable and custom redundant resource330 that can be activated and dynamically assigned to either of theprimary chips 101 if a primary unit 320 in either of the primary devicelayers 101 becomes faulty during system runtime. Also, if the primaryunits 320 in both primary chips 101 become faulty, the configurableredundant resource 330 on the secondary chip 102 can be used to replaceboth, albeit at a reduced system performance.

The additional device layer 102 includes the reliability/variabilitycontroller 116, with high-bandwidth and low-latency access to the restof the chip. The reliability/variability controller 116 performs regularchecks on the existing hardware in order to detect potential faults asin the flow chart of FIG. 4. When a fault is detected, the controller116 then uses the pre-programmed recovery schemes 500, like the exampleshown in FIG. 5, to recover from the fault. Recovery schemes can beimplemented as a lookup table with the manufacturers preset recoveryschemes. Each recovery scheme indicates precisely how to recover fromspecific faults using the existing redundancy in the second devicelayer. In the cases that the exact replica of the faulty unit is notavailable, the controller uses configurable hardware blocks such asprogrammable logic arrays for emulating the desired functionality. Theauxiliary device layer also includes configurable routing, additionalcache hierarchy in the form of SRAM or DRAM, configurable logic blocksand ASIC macros.

On-chip recovery schemes compensate for the changes in the configurablelogic timing in general, which creates major problems in maintaining thesame synchronous timing. The on-chip reliability/variability controllerrecovery scheme adjusts the clock frequency in both the first and secondlayers so that the two layers can still be synchronous.

The on-chip reliability/variability controller 116 may select from anumber of preset recovery schemes 500 depending on a number ofconditions including: the power overhead of a recovery scheme, thecurrent power saving mode, the frequency target for both layers,severity of fault, and current workload demand. It is notable that therecovery scheme can be changed in time, when one or more of theseconditions change. For instance: the reliability/variability controllermay opt for a high-performance high-overhead recovery scheme when theworkload demand is high. Later when the workload demand drops, thisrecovery scheme is deactivated and a low-power low-overhead scheme isused. This way the controller 116 makes efficient use of the on-chipresources even for fault recovery or variability issues.

The reliability/variability controller 116 monitors the devices in boththe first and second layer for variability problems as well as lifetimereliability problems. Variability problems can be of static or dynamicnature, as follows:

For static variability problems such as atomic dopant variations,lithographic variations etc.; the controller assesses the variability bychecking the performance, power and temperature of units on theprocessor. In these cases, number of cores may have inherently higherleakage power dissipation and temperatures (due to lower V_(th) forinstance). The cores affected by process variability are speciallytreated by the on-chip controller 116 in terms of clock frequencysettings, compensating for the increased temperatures etc.

For other cases where the variability issues change in time, such asNBTI (Negative Bias Temperature Shifts) problems, the controllerperforms constant checks at regular intervals to detect these atruntime, as well as compensating for these problems as they occur.

The on-chip controller 116 may include a lookup table 500 as shown inFIG. 5 with various recovery schemes for different types of faults.These schemes are provided and programmed by the manufacturer for eachfault in the critical parts of the process. The schemes includeinformation about:

Replica availability 530: Whether the exact replica for the custom blockis available at the top/bottom layer. This makes the recovery muchsimpler by activating the needed replica only.

Options 520: Whether there are multiple recovery options possible. Insome cases, there are various ways of recovering from the fault.However, each solution varies in terms of resulting performance, powerdissipation, routing overhead etc. The controller is provided with thisinformation so that it can select between different schemes depending onthe operating conditions: such as workload demand, power dissipationrestrictions, and performance constraints. Later when the conditionschange, the controller can dynamically choose another scheme to activatewith more desirable characteristics for the new conditions. (Forinstance, if the workload demand is high when the fault appears, thecontroller selects a high-performance recovery solution). Later when theworkload demand is reduced, the controller opts for a low powerrecovery).

Activation List 540: The recovery scheme specifies which blocks need tobe used for each recovery scheme. The possibilities include exactreplicas, configurable blocks, and generic blocks.

Target IPC/Frequency 550: Each recovery scheme is bound to operate at aspecific frequency that is set by the manufacturer. Some schemes thatrecover from multiple faults need a reduced clock frequency to toleratemany redundancy blocks including configurable ones to be activated.Hence the target IPC is lower for these cases. However, the presetschemes also include additional performance boost schemes thatcompensate from the performance reduction from the reduced frequencyrecovery schemes. The performance boost is achieved through activatingmore execution units, configuring sizes of the processor resources tolarger numbers and activating caches. Hence even with lower frequency onboth layers the overall chip performance can be improved with the faultrecovery scheme.

Rerouting path 560: the on-chip controller is provided with exactrerouting path to connect the redundancies such that the resultingelements will work synchronously as specified by the manufacturer.

Power overhead 570: Each recovery scheme that incorporates more than theexact replica is bound to have power dissipation overhead. Thecontroller is provided with this information so that the proper powersaving mode is selected for proper operation.

Referring to FIG. 6, a schematic representation of the chip stackingprocess of the present invention is shown. Base semiconductor chips 100are formed on a first semiconductor substrate 8 employing manufacturingmethods known in the art. Typically, the first semiconductor substrate 8has a diameter from about 150 mm to about 300 mm, and comprises silicon.The sides of the base semiconductor chips 100 may have a dimension fromabout 10 mm to about 30 mm, although lesser and greater dimensions arealso contemplated herein. Thus, the first semiconductor substrate 8 mayinclude from about 15 to about 700 base semiconductor chips 100depending on the relative size of the base semiconductor chips 100 andthe first semiconductor substrate 8.

Each base semiconductor chip 100 includes a plurality of chiplets. Thus,each base semiconductor chip 100 is a multi-chiplet semiconductor chip.The plurality of chiplets collectively provides the full functionalityof a base semiconductor chip 100. The plurality of chiplets includes atleast two non-identical chiplets, which provide different functions in abase semiconductor chip 100. For example, the plurality of chiplets mayinclude a logic chiplet performing logic functions and a memory chipletproviding memory functions to the logic chiplet. Each base semiconductorchip 100 is designed to provide the functionality of a fully functionalindependent chip that may be packaged as a fully functional module.

Non-limiting examples of the types of chiplets within a basesemiconductor chip 100 include a processor core chiplet, a static randomaccess memory (SRAM) chiplet, an embedded dynamic random access memory(eDRAM) chiplet, a cache memory chiplet, a non-volatile memory chiplet,a programmable gate array (PGA) chiplet, a peripheral circuitry chiplet,an input/output control chiplet, a built-in-self-test (BIST) chiplet, amemory controller chiplet, a power supply bus chiplet, a ground buschiplet, and a signal bus chiplet.

For example, a base semiconductor chip 100 may include a first-typechiplet 40 and three second-type chiplets 60. The first-type chiplet 40may be a logic chiplet and the three second-type chiplets 60 may be amemory chiplet. While the present invention is described with a basesemiconductor chip 100 having one first-type chiplet 40 and threesecond-type chiplets 60, the present invention may be practiced on anybase semiconductor chip.

Once processing on the first semiconductor substrate 8 is complete, thebase semiconductor chips 100 are diced and sorted based on test results.Testing on the base semiconductor chips 100 may be performed prior toand/or after dicing of the first semiconductor substrate 8 into multiplebase semiconductor chips 100. The base semiconductor chips 100 aresorted based on the test results. Fully functional units of the basesemiconductor chips 100, in which all of the plurality of chiplets arefully functional, may be packaged as a functional semiconductor module,which provides the full functionality of the base semiconductor chips100 as originally designed. For example, each of the fully functionalunits of the base semiconductor chips 100 may include a functionalfirst-type chiplet 49 and three of functional second-type chiplets 69.

Some of the base semiconductor chips 100 are not fully functional asoriginally designed. This may occur if any one of the chiplets in a basesemiconductor chip 100 is non-functional, or less than fully functionalin any way. Here, the term “non-functional” refers to any deficiency inthe functionality of each chiplet from the design specification of thechiplet, i.e., any deviation from the expected performance of eachchiplet based on the design.

For example, a base semiconductor chip 100 may include a non-functionalfirst-type chiplet 41 and a non-functional second-type chiplet 61. Inthis case, the base semiconductor chip 100 does not have thefunctionality that the base semiconductor chip 100 is designed toprovide, i.e., the base-semiconductor chip 100 is non-functional. Suchnon-functional units of the base semiconductor chips 100 are identifiedwhen test data indicates that at least one chiplet in these units of thebase semiconductor chips 100 is non-functional. Thus, testing of thesemiconductor chips 100 is followed by sorting of the base semiconductorchips 100 into functional units and non-functional units. The functionalunits may be packaged into modules as described above, and thenon-functional units may be sorted into various bins depending on theseverity of the non-functionality to determine whether repair ispossible.

According to the present invention, the non-functional units of the basesemiconductor chips 100 that are deemed to be repairable are repaired byproviding at least one repair semiconductor chips that are subsequentlystacked to compensate for the deficiency in functionality of eachnon-functional unit of the base semiconductor chips 100.

In one embodiment, each of the semiconductor chiplet in the repairsemiconductor chip may have substantially the same design layout as oneof the plurality of chiplets on the base semiconductor substrate 100. Inone case, the repair semiconductor chiplet may be the semiconductorchiplet that has substantially the same design layout as one of theplurality of chiplets on the base semiconductor substrate 100.

In another embodiment, the design layout of each of the semiconductorchiplet in the repair semiconductor chip may be a mirror image of thedesign layout of one of the plurality of chiplets on the basesemiconductor substrate 100. In one case, the repair semiconductorchiplet may be the semiconductor chiplet that has a design layout whichis a mirror image of one of the plurality of chiplets on the basesemiconductor substrate 100.

The repair semiconductor chips may be manufactured on differentsemiconductor substrates. A plurality of semiconductor substrates may beemployed to provide different types of repair semiconductor chips.Alternately, repair chips of different types may be manufactured on thesame semiconductor substrate by employing a set of reticles thatincludes images for multiple types of repair chips. Each repairsemiconductor chiplet includes a semiconductor chiplet that provides thesame functionality as one of the plurality of chiplets on a basesemiconductor substrate 100 is designed to provide. In one case, arepair semiconductor chiplet is a semiconductor chiplet that providesthe same functionality as one of the plurality of chiplets on a basesemiconductor substrate 100 is designed to provide.

For example, first-type repair semiconductor chips 150 may be formed ona second semiconductor substrate 108, and second type repairsemiconductor chips 250 may be formed on a third semiconductor substrate208.

The first-type repair semiconductor chips 150 may have substantially thesame design layout as a first-type chiplet 40. In one case, each of thefirst-type repair semiconductor chips 150 may be the same as thefirst-type chiplet 40. Alternately, the design layout of the first-typerepair semiconductor chips 150 may be a mirror image of the first-typechiplet 40. In one case, the design layout for the first-type repairsemiconductor chips 150 may be the mirror image of the first-typechiplet 40.

Likewise, the second-type repair semiconductor chips 250 may havesubstantially the same design layout as a second-type chiplet 60. In onecase, each of the second-type repair semiconductor chips 250 may be thesame as the second-type chiplet 60. Alternately, the design layout ofthe second-type repair semiconductor chips 250 may be a mirror image ofthe second-type chiplet 60. In one case, the design layout for thesecond-type repair semiconductor chips 250 may be the mirror image ofthe second-type chiplet 60.

Once the first-type repair semiconductor chips 150 are manufactured, thesecond semiconductor substrate 108 is diced to separate the first-typerepair semiconductor chips 150. The first-type repair semiconductorchips 150 are tested, prior to and/or after dicing, to test thefunctionality of each unit. The first-type repair semiconductor chips150 are sorted into functional first-type repair semiconductor chips 190and non-functional first-type repair semiconductor chips 110. Thenon-functional first-type repair semiconductor chips 110 are discarded.

A functional first-type repair semiconductor chip 190 is stackeddirectly on one of the base semiconductor chip 100 which include anon-functional first-type chiplet 41. The functional first-type repairsemiconductor chip 190 and the base semiconductor chip 100 forms amulti-chip assembly, in which the deficiency in the functionality of thebase semiconductor chip 100 due to the non-functional first-type chiplet41 is compensated by the functional first-type repair semiconductorchip. The functional first-type repair semiconductor chip 190 may bestacked above or below the base semiconductor chip 100 depending on thedesign and presence of inter-chip connection elements such as ControlledCollapse Chip Connection (C4) bonding pads and/or through substratevias.

In case the base semiconductor chip 100 further comprises anon-functional second-type chiplet 61, a functional unit of thesecond-type repair semiconductor chips 250 is stacked to compensate forthe deficiency in the functionality of the base semiconductor chip 100due to the non-functional second-type chiplet 61.

For this purpose, once the second-type repair semiconductor chips 250are manufactured, the third semiconductor substrate 208 is diced toseparate the second-type repair semiconductor chips 250. The second-typerepair semiconductor chips 250 are tested, prior to and/or after dicing,to test the functionality of each unit. The second-type repairsemiconductor chips 250 are sorted into functional second-type repairsemiconductor chips 290 and non-functional first-type repairsemiconductor chips 210. The non-functional first-type repairsemiconductor chips 210 are discarded.

A functional second-type repair semiconductor chip 290 is verticallystacked to the multi-chip assembly of the base semiconductor chip 100and the functional first-type repair semiconductor chip 190. Themulti-chip assembly thus grows to include the base semiconductor chip100, the functional first-type repair semiconductor chip 190, and thefunctional second-type repair semiconductor chip 290. The functionalsecond-type repair semiconductor chip 290 may be stacked above or belowthe base semiconductor chip 100 depending on the design and presence ofinter-chip connection elements such as Controlled Collapse ChipConnection (C4) bonding pads and/or through substrate vias.

The above process may be repeated until the functional deficiency causedby each of the non-functional chiplets in the base semiconductor chip100 is cured by the stacking of additional repair semiconductor chips.The multi-chip assembly including at least the base semiconductor chip100, the functional first-type repair semiconductor chip 190, and thefunctional second-type repair semiconductor chip 290 provides the samefunctionality as a functional base semiconductor chip, i.e., the samefunctionality as the base semiconductor chip 100 is designed to provide.

Referring to FIG. 7, a flow diagram illustrating the processing steps ofthe present invention is shown. Referring to step 5, at least onemulti-chiplet semiconductor chip is manufactured. Each of the at leastone multi-chiplet semiconductor chip is a semiconductor chip thatcontains at least two chiplets of different types. Each of the at leastone multi-chiplet semiconductor chip may be one of the basesemiconductor chips 100 in FIG. 6. The different types of chipletswithin each of the at least one multi-chiplet semiconductor chip may bethe types of chiplets that may be employed for the base semiconductorchip 100 described above. The at least one multi-chiplet semiconductorchip may be manufactured on the same semiconductor substrate and dicedas described above.

Referring to step 15, each of the at least one multi-chipletsemiconductor chip is tested after completion of manufacturing steps.Particularly, each chiplet is tested for functionality in each of theleast one multi-chiplet semiconductor chip.

Referring to step 25, the test results are analyzed for each of the atleast one multi-chiplet semiconductor chip to determine whether eachmulti-chiplet semiconductor chip is functional or non-functional.

If the multi-chiplet semiconductor chip is functional, a functionalmulti-chiplet semiconductor chip is provided as shown at step 35, i.e.,the multi-chiplet semiconductor chip may be used as is. The functionalmulti-chiplet semiconductor chip may be packaged into a module or may beemployed in any other suitable manner.

If the multi-chiplet semiconductor chip is non-functional,non-functional chiplets are identified by analyzing the test data asshown at step 45.

Referring to step 55, at least one functional repair semiconductor chip,such as the functional first-type repair semiconductor chip 190 and thefunctional second-type repair semiconductor chip 290 in FIG. 6, isattached to the multi-chiplet semiconductor chip to compensate for thefunctional deficiency in the multi-chiplet semiconductor chip that iscaused by the non-functional chiplets. As described in FIG. 6, the atleast one functional repair semiconductor chip may be pre-tested and/orsorted to insure the functionality prior to being attached to themulti-chiplet semiconductor chip.

The attachment of the at least one functional repair semiconductor chipto the multi-chiplet semiconductor chip is effected by vertical stackingof chips. Each of the at least one functional repair semiconductor chipmay be stacked above or below the multi-chiplet semiconductor chipdepending on the design and presence of inter-chip connection elementssuch as Controlled Collapse Chip Connection (C4) bonding pads and/orthrough substrate vias and/or other inter-layer connection technologies.A multi-chip assembly of the multi-chiplet semiconductor chip and the atleast one functional repair semiconductor chip is formed. The scheme mayuse on-chip BIST structures and on-chip controller, embedded in both thebase and repair chiplets, to activate the functional redundancies in therepair chip.

While the general stacking of the at least one repair chiplet onto themulti-chiplet semiconductor was discussed above broadly, there may atleast be additional resources and steps necessary to activate theexisting infrastructure for the scheme to operate. Such additionalresources and steps may include the thinning of the silicon to exposethe through-silicon-via leads that connect the base chip to the repairchip, controller macros and multiplexers, and the provision of fuses foractivating the repair chip and deactivating the base chip. Also, oneskilled in the art may observe that the repair chip referred to in thediscussion above can be manufactured separately, or can be used frompartial good dies with functioning parts below a preset threshold.

Referring to step 65, the multi-chip assembly is tested forfunctionality. Unless the chip stacking process is defective andintroduces improper electrical connection, the multi-chip assembly isfunctional and fully operational.

If the multi-chip assembly is functional as shown at step 75, themulti-chip assembly provides functionality of a fully functionalmulti-chiplet semiconductor chip. The multi-chip assembly may be used inthe same manner as a functional multi-chiplet semiconductor chip, i.e.,the multi-chip assembly of the multi-chiplet semiconductor chip and theat least one repair semiconductor chip may be packaged into a module ormay be employed in any other suitable manner.

If the multi-chip assembly is non-functional for any reason as shown atstep 85, non-functional repair semiconductor chips are identified byanalyzing the test data. An additional repair semiconductor chip isattached to the multi-chip semiconductor chip or to the repairsemiconductor chip by vertical stacking. The process of step 75 isrepeated for the chiplet for which the functionality has not beenrestored at this point to continue to repair the multi-chipletsemiconductor chip until a fully functional multi-chip assembly isformed.

Referring to FIG. 8A, a base semiconductor chip 100 according to a firstembodiment of the present invention includes a non-functional first-typechiplet 41, a non-functional second-type chiplet 61, two functionalsecond-type chiplets 69. The base semiconductor chip 100 may alsoinclude inter-chiplet regions 10 that separate the chiplets (41, 61,69). A set of through-substrate vias 97 may be provided in each of thechiplets (41, 61, 91) in the base semiconductor chip 100. To compensatefor the deficiency in the functionality of the base semiconductor chip100 due to the non-functional chiplets, i.e., the non-functionalfirst-type chiplet 41 and the non-functional second-type chiplet 61, afunctional first-type repair semiconductor chip 190 and a functionalsecond-type repair semiconductor chip 290 are stacked directly on thenon-functional first-type chiplet 41 and the non-functional second-typechiplet 61, respectively. The functional first-type repair semiconductorchip 190 includes a functional first-type chiplet 49. The functionalsecond-type repair semiconductor chip 290 includes a functionalsecond-type chiplet 69. Each of the functional first-type repairsemiconductor chip 190 and the functional second-type repairsemiconductor chip 290 includes a set of through-substrate vias 97 thatprovides electrical connection with the base semiconductor chip 100.

Referring to FIG. 8B, a first exemplary multi-chip assembly 400 isformed by vertically stacking the base semiconductor chip 100 and thefunctional first-type repair semiconductor chip 190 and the functionalsecond-type repair semiconductor chip 290. The set of through-substratevias 97 embedded in the functional first-type repair semiconductor chip190 provides electrical connection between the functional first-typechiplet 49 in the functional first-type repair semiconductor chip 190and the base semiconductor chip 100. Typically, programmable devices inthe base semiconductor chip 100 such as electrical fuses are employed toset the logic of the base semiconductor chip 100 to bypass thenon-functional first-type chiplet 41 and to employ the functionalfirst-type chiplet 49 in the functional first-type repair semiconductorchip 190 instead.

Likewise, the set of through-substrate vias 97 embedded in thefunctional second-type repair semiconductor chip 290 provides electricalconnection between the functional second-type chiplet 69 in thefunctional second-type repair semiconductor chip 290 and the basesemiconductor chip 100. Typically, programmable devices in the basesemiconductor chip 100 such as electrical fuses are employed to set thelogic of the base semiconductor chip 100 to bypass the non-functionalsecond-type chiplet 61 and to employ the functional second-type chiplet69 in the functional second-type repair semiconductor chip 190 instead.

In case a set of through substrate vias 97 is used to vertically stack arepair semiconductor chip such as the functional first-type repairsemiconductor chip 190 and the functional second-type repairsemiconductor chip 290 with the base semiconductor chip 100, the repairsemiconductor chip may include a functional chiplet that hassubstantially the same design as a non-functional chiplet in the basesemiconductor layer 100. For example, the functional first-type chiplet49 located in the functional first-type repair semiconductor chip 190may have the same design as the non-functional first-type chiplet 41,and the functional second-type chiplet 69 located in the functionalsecond-type repair semiconductor chip 290 may have the same design asthe non-functional second-type chiplet 61.

The functional first-type repair semiconductor chip 190 may include thefunctional first-type chiplet 49 and additional peripheral circuits ordevices, or may consist of the functional first-type chiplet 49 whichhas substantially the same design as the non-functional first-typechiplet 41. Likewise, the functional second-type repair semiconductorchip 290 may include the functional second-type chiplet 69 andadditional peripheral circuits or devices, or may consist of thefunctional second-type chiplet 69 which has substantially the samedesign as the non-functional second-type chiplet 61.

Referring to FIG. 9A, a base semiconductor chip 100 according to asecond embodiment of the present invention includes a non-functionalfirst-type chiplet 41, a non-functional second-type chiplet 61, twofunctional second-type chiplets 69. The base semiconductor chip 100 mayalso include inter-chiplet regions 10 that separate the chiplets (41,61, 69). To compensate for the deficiency in the functionality of thebase semiconductor chip 100 due to the non-functional chiplets, i.e.,the non-functional first-type chiplet 41 and the non-functionalsecond-type chiplet 61, a functional first-type repair semiconductorchip 190 and a functional second-type repair semiconductor chip 290 arestacked directly on the non-functional first-type chiplet 41 and thenon-functional second-type chiplet 61, respectively. The functionalfirst-type repair semiconductor chip 190 includes a functionalfirst-type chiplet 49. The functional second-type repair semiconductorchip 290 includes a functional second-type chiplet 69.

The upper surface of the non-functional first-type chiplet 41 and thelower surface of the functional first-type repair semiconductor chip 190include sets of embedded C4 pads having a matched pattern. The uppersurface of the non-functional second-type chiplet 61 and the lowersurface of the functional second-type repair semiconductor chip 290include additional sets of embedded C4 pads and/or similar inter-layerinterconnect technologies having a matched pattern. Optionally, a set ofthrough-substrate vias (not shown) may be provided in each of thechiplets (41, 61, 91) on the bottom side the base semiconductor chip100. Optionally, the functional first-type repair semiconductor chip 190and/or the functional second-type repair semiconductor chip 290 mayinclude a set of through-substrate vias (not shown) on their topsurfaces.

Referring to FIG. 9B, a second exemplary multi-chip assembly 500 isformed by vertically stacking the base semiconductor chip 100 and thefunctional first-type repair semiconductor chip 190 and the functionalsecond-type repair semiconductor chip 290. The embedded C4 pads (notshown) located on the bottom surface of the functional first-type repairsemiconductor chip 190 and the embedded C4 pads (not shown) located onthe top surface of the non-functional first-type chiplet 41 provideselectrical connection between the functional first-type chiplet 49 inthe functional first-type repair semiconductor chip 190 and the basesemiconductor chip 100 through an array of C4 balls (not shown).Typically, programmable devices in the base semiconductor chip 100 suchas electrical fuses are employed to set the logic of the basesemiconductor chip 100 to bypass the non-functional first-type chiplet41 and to employ the functional first-type chiplet 49 in the functionalfirst-type repair semiconductor chip 190 instead.

Likewise, the embedded C4 pads (not shown) located on the bottom surfaceof the functional second-type repair semiconductor chip 290 and theembedded C4 pads (not shown) located on the top surface of thenon-functional second-type chiplet 61 provides electrical connectionbetween the functional second-type chiplet 69 in the functionalsecond-type repair semiconductor chip 290 and the base semiconductorchip 100 through another array of C4 balls (not shown). Typically,programmable devices in the base semiconductor chip 100 such aselectrical fuses are employed to set the logic of the base semiconductorchip 100 to bypass the non-functional second-type chiplet 61 and toemploy the functional second-type chiplet 69 in the functionalsecond-type repair semiconductor chip 290 instead.

Embedded C4 pads and balls are used as basic examples throughout allembodiments. However, the schemes are not limited to this specifictechnology (wire-bonding, metal-metal, oxide-oxide bonding, etc).Alternative inter-layer bonding techniques may be used in a similarfashion.

In case an array of C4 balls and accompanying C4 pads are used tovertically stack a repair semiconductor chip such as the functionalfirst-type repair semiconductor chip 190 and the functional second-typerepair semiconductor chip 290 with the base semiconductor chip 100, therepair semiconductor chip may include a functional chiplet that has amirror image design of the design of a non-functional chiplet in thebase semiconductor layer 100. For example, design of the functionalfirst-type chiplet 49 located in the functional first-type repairsemiconductor chip 190 may be a mirror image design of thenon-functional first-type chiplet 41, and design of the functionalsecond-type chiplet 69 located in the functional second-type repairsemiconductor chip 290 may a mirror image design of the non-functionalsecond-type chiplet 61. When vertically stacked through the arrays of C4balls, functionally equivalent portions are matched across thefunctional first-type chiplet 49 and the non-functional first-typechiplet 41 and across the functional second-type chiplet 69 and thenon-functional second-type chiplet 61.

The functional first-type repair semiconductor chip 190 may include thefunctional first-type chiplet 49 and additional peripheral circuits ordevices, or may consist of the functional first-type chiplet 49 whichhas substantially the same design as the non-functional first-typechiplet 41. Likewise, the functional second-type repair semiconductorchip 290 may include the functional second-type chiplet 69 andadditional peripheral circuits or devices, or may consist of thefunctional second-type chiplet 69 which has substantially the samedesign as the non-functional second-type chiplet 61.

In some cases, the multi-chip assembly of the base semiconductor chip100 and the functional first-type repair semiconductor chip 190 and thefunctional second-type repair semiconductor chip 290 may not befunctional, for example, for exceeding overlay specification during thestacking or defective processing steps during C4 bonding, etc. This casecorresponds to step 85 of the flow diagram in FIG. 7. Additional repairmay be attempted by vertically stacking at least one additional repairsemiconductor chip on the base semiconductor chip 100 or any of thefunctional first-type repair semiconductor chip 190 and the functionalsecond-type repair semiconductor chip 290.

Referring to FIG. 10A, a defective exemplary multi-chip assembly 400′ ofthe present invention may be formed employing the methods for formingthe first exemplary multi-chip assembly 400 of the first embodiment ofthe present invention. Upon testing after forming the first multi-chipassembly 400, however, the “functional second-type repair semiconductorchip 290” does not provide the functionality of a “functionalsecond-type chiplet 69” in this case, thereby rendering the firstmulti-chip assembly 400 defective, i.e., not providing the functionalityof a fully functional base semiconductor chip. For the failure toprovide the expected functionality, the first multi-chip assembly 400 isherein termed the defective exemplary multi-chip assembly 400′ in thiscase. The defective unit of the “functional second-type chiplet 69” isherein termed a defective second-type chiplet 69X. The defect unit ofthe “functional second-type repair semiconductor chip 290” is hereintermed a defective second-type repair semiconductor chip 290X.

Referring to FIG. 10A, which shows a third embodiment of the presentinvention, the defect in the functionality of the defective exemplarymulti-chip assembly 400′ may be cured by vertically stacking anotherfunctional second-type repair semiconductor chip 290 with the defectiveexemplary multi-chip assembly 400′. The functional second-type repairsemiconductor chip 290 provides the functionality that thenon-functional second-type chiplet 61 and the defective second-typechiplet 69X collectively fail to provide to the base semiconductor chip100.

Referring to FIG. 10B, a third exemplary multi-chip assembly 600comprises a vertical stack of the defective exemplary multi-chipassembly 400′ and the functional second-type repair semiconductor chip290. The third exemplary multi-chip assembly 600 includes the basesemiconductor chip 100, the functional first-type chiplet 49, thedefective second-type chiplet 69X, and the functional second-typechiplet 69. Typically, programmable devices in the base semiconductorchip 100 such as electrical fuses are employed to set the logic of thebase semiconductor chip 100 to bypass the non-functional second-typechiplet 61 and the defective second-type chiplet 69, and to employ thefunctional second-type chiplet 69 in the functional second-type repairsemiconductor chip 290 instead. The third exemplary multi-chip assembly600 provides the same functionality as the base semiconductor chip 100is designed to provide, or the functionality that a fully functionalbase semiconductor chip would provide.

In this case, at least two repair semiconductor chips are verticallystacked directly above and/or below a non-functional chiplet of the basesemiconductor chip. For example, the defective second-type repairsemiconductor chips 290X and the functional second-type repairsemiconductor chip 290 are repair semiconductor chips. Each of the atleast two repair semiconductor chip includes a chiplet designed toprovide the same functionality as the non-functional chiplet in the basesemiconductor chip. For example, the defective second-type repairsemiconductor chips 290X includes the defective second-type chiplet 69Xwhich is designed to provide the same functionality as thenon-functional second-type chiplet 61, and the functional second-typerepair semiconductor chip 290 includes the functional second-typechiplet 69 which is designed to provide the same functionality as thenon-functional second-type chiplet 61.

The at least two repair semiconductor chips are stacked by sets ofthrough-substrate vias 97, which are embedded in the substrate of thebase semiconductor chip 100 and the at least two repair semiconductorchips. For example, the defective second-type repair semiconductor chip290X and the functional second-type repair semiconductor chip 290 arestacked by sets of through-substrate vias 97, which are embedded in thesubstrate of the base semiconductor chip 100, the defective second-typerepair semiconductor chip 290X, and the functional second-type repairsemiconductor chip 290.

While the present invention is described with a defective second-typerepair semiconductor chip 290X located above the non-functionalsecond-type chiplet 61 and a functional second-type repair semiconductorchip 290 located below the non-functional second-type chiplet 61,embodiments in which the locations of the defective second-type repairsemiconductor chip 290X and the functional second-type repairsemiconductor chip 290 are exchanged are explicitly contemplated herein.Further, embodiments in which the defective second-type repairsemiconductor chip 290X and the functional second-type repairsemiconductor chip 290 are located above the non-functional second-typechiplet 61 are explicitly contemplated herein. Yet further, embodimentsin which the defective second-type repair semiconductor chip 290X andthe functional second-type repair semiconductor chip 290 are locatedbelow the non-functional second-type chiplet 61 are also explicitlycontemplated herein. Still further, embodiments in which more than twoof the “functional second-type repair semiconductor chip 290” arevertically stacked on the non-functional second-type chiplet 61 in whichsome of the “functional second-type repair semiconductor chip 290” aresubsequently tested to be defective second-type repair semiconductorchips 290X, while one is a functional unit of the “functionalsecond-type repair semiconductor chips 290” are explicitly contemplatedherein. Even further, embodiments in which multiple types of repairsemiconductor chips are vertically stacked are explicitly contemplatedherein.

Referring to FIG. 11A, which shows a fourth embodiment of the presentinvention, another defective exemplary multi-chip assembly 500′comprises a defective second-type repair semiconductor chip 290Xincluding defective second-type chiplet 69X. The other defectiveexemplary multi-chip assembly 500′ may be formed in the same manner asthe second exemplary multi-chip assembly 500 of the second embodiment ofthe present invention. Upon testing after formation of a secondexemplary multi-chip assembly 500, a “functional second-type repairsemiconductor chips 290” is tested to be non-functional, i.e., thedefective second-type repair semiconductor chip 290X.

The defect in the other defective exemplary multi-chip assembly 500′ maybe cured by vertically stacking another functional second-type repairsemiconductor chip 290 with the other defective exemplary multi-chipassembly 500′. The functional second-type repair semiconductor chip 290provides the functionality that the non-functional second-type chiplet61 and the defective second-type chiplet 69X collectively fail toprovide to the base semiconductor chip 100.

Referring to FIG. 11B, a fourth exemplary multi-chip assembly 700comprises a vertical stack of the other defective exemplary multi-chipassembly 500′ and the functional second-type repair semiconductor chip290. The fourth exemplary multi-chip assembly 700 includes the basesemiconductor chip 100, the functional first-type chiplet 49, thedefective second-type chiplet 69X, and the functional second-typechiplet 69. Typically, programmable devices in the base semiconductorchip 100 such as electrical fuses are employed to set the logic of thebase semiconductor chip 100 to bypass the non-functional second-typechiplet 61 and the defective second-type chiplet 69, and to employ thefunctional second-type chiplet 69 in the functional second-type repairsemiconductor chip 290 instead. The fourth exemplary multi-chip assembly700 provides the same functionality as the base semiconductor chip 100is designed to provide, or the functionality that a fully functionalbase semiconductor chip would provide.

In this case, at least two repair semiconductor chips are verticallystacked directly above and/or below a non-functional chiplet of the basesemiconductor chip. For example, the defective second-type repairsemiconductor chips 290X and the functional second-type repairsemiconductor chip 290 are repair semiconductor chips. Each of the atleast two repair semiconductor chip includes a chiplet designed toprovide the same functionality as the non-functional chiplet in the basesemiconductor chip. For example, the defective second-type repairsemiconductor chips 290X includes the defective second-type chiplet 69Xwhich is designed to provide the same functionality as thenon-functional second-type chiplet 61, and the functional second-typerepair semiconductor chip 290 includes the functional second-typechiplet 69 which is designed to provide the same functionality as thenon-functional second-type chiplet 61.

One of the at least two repair semiconductor chips is stacked directlyabove the base semiconductor chip by C4 bonding, and another of the atleast two repair semiconductor chips is stacked below the basesemiconductor chip 100 by a set of through-substrate vias 97, which isembedded in the substrate of the base semiconductor chip 100. Forexample, the defective second-type repair semiconductor chips 290X isstacked directly above the base semiconductor chip by C4 bonding, andthe functional second-type repair semiconductor chip 290 is stackedbelow the base semiconductor chip 100 by a set of through-substrate vias97, which is embedded in the substrate of the base semiconductor chip100.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present invention. It is therefore intended that the presentinvention not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A method of forming a multi-chip assemblycomprising: testing base semiconductor chips to identify a basesemiconductor chip having less than a fully operational functionalitythat said at least one base semiconductor chip is designed for, whereinsaid identified base semiconductor chip comprises a non-functionalchiplet and a functional chiplet having a coplanar top surface, whereinsaid non-functional chiplet does not provide a first functionality thatsaid non-functional chiplet is designed for, and said functional chipletprovides a second functionality that said functional chiplet is designedfor, said second functionality being different from said firstfunctionality, and said fully operational functionality includes atleast said first functionality and said second functionality; verticallystacking a repair semiconductor chip on or beneath said non-functionalchiplet to form a multi-chip assembly, said repair semiconductor chiphaving said first functionality, and said functional chiplet does notoverlie or underlie any semiconductor chip; and activating functionalredundancies in said repair semiconductor chip employing a devicelocated in said base semiconductor chip, wherein said repairsemiconductor chip is configured to provide said first functionality tosaid multi-chip assembly upon activation of said functional redundanciesso that said multi-chip assembly has exactly said fully operationalfunctionality.
 2. The method of claim 1, wherein said repairsemiconductor chip has substantially the same design layout as saidnon-functional chiplet.
 3. The method of claim 1, wherein said repairsemiconductor chip includes a set of through-substrate vias formedwithin a substrate, wherein said set of through-substrate vias provideselectrical connection between said repair semiconductor chip and saidnon-functional chiplet.
 4. The method of claim 1, further comprising:testing said multi-chip assembly after said vertically stacking saidrepair semiconductor chip on or beneath said non-functional chiplet todetermine if said multi-chip assembly provides said fully operationalfunctionality; and upon determination that said multi-chip assembly doesnot provide said fully operational functionality, vertically stackinganother repair semiconductor chip beneath or on said multi-chip assemblyto form a modified multi-chip assembly, wherein at least two repairsemiconductor chips are vertically stacked directly above and/or belowsaid non-functional chiplet; and activating functional redundancies insaid other repair semiconductor chip employing said device or anotherdevice located in said base semiconductor chip, wherein said otherrepair semiconductor chip is configured to provide said firstfunctionality to said modified multi-chip assembly upon activation ofsaid functional redundancies in said other repair semiconductor chip sothat said modified multi-chip assembly has exactly said fullyoperational functionality.